Many attempts have been made to create a material with high absorption/adsorption capacity, including the creation of oleophilic and hydrophobic materials which will preferentially absorb oils and oil-like compounds over water. As used herein, absorption refers to the process of taking something in through pores or interstices, and adsorption refers to the accumulation of gases, liquids or solids on the surface of a solid or liquid. A specific example of such a material and its associated manufacturing process is disclosed in U.S. Pat. No. 5,110,785 issued May 5, 1992 to Reed et al. for “Composition of Matter and Method of Making” (the '785 patent”). Reed and his colleague disclose a process in which material is heated to a temperature between 280° C. and 380° C. for approximately 10 minutes to create a hydrophobic particle capable of floating on water for extended periods of time and which can absorb up to 3.5 times its own weight in oil. However, due to the low temperature and short heating time inherent in the process cycle of the '785 disclosure, the resultant material has a relatively small internal surface area which substantially limits its absorption/adsorption capacity. Similarly, the resultant material as described has not been brought to substantially high carbon content to be made inorganic or biologically unavailable.
Other efforts have focused upon the use of activated carbon for such remediation efforts due to its high internal surface area and ability to absorb/adsorb large amounts of a chemical substance. However, activated carbon does not preferentially select oil over water so that an activated carbon used in an environment with both non-polar and polar molecules will absorb polar molecules readily, thereby decreasing its effectiveness for oil removal. Moreover, activated carbon must be produced and/or regenerated at high temperatures under special conditions, thereby rendering it expensive to produce, especially at small scale.
More recently, U.S. Pat. No. 7,470,725 issued Dec. 30, 2008 to Schwertfeger et al. for “Organically Modified Aerogels” discloses a method for making surface-modified aero gels for use in the afore-mentioned and other applications. However, synthetic materials may not be left safely in the environment without risk that they will contribute to further contamination thereof, and accordingly, afford less than optimal solutions to the environmental contamination problem. Additionally, the production of said aero gel-s requires the use of strong acids and bases, which present an additional hazard in waste disposal.
U.S. Pat. No. 6,326,070 issued Dec. 4, 2001 to Sodergren for “Absorption Means” discloses a method for removing terpene content from sawdust and coating the sawdust with Teflon. The coating of the particle with Teflon increases oil absorption capacity while making the particle hydrophobic. However, because the material does not undergo pyrolysis, the total absorptive capacity is not increased. Moreover, because the particle is coated in polytetrafluoroethylene, it cannot be safely left in the environment or incinerated without releasing fluorine into the environment.
U.S. Pat. No. 5,585,319 issued Dec. 17, 1996 to Saitoh et al. for “Process For Preparing Oil Sorbent And Device For Continuously Making The Same” discloses a method similar to the method disclosed by Reed et al. in the '785 patent. Saitoh et al. disclose a material preparation process and apparatus wherein material is heated to a temperature in the range of 250°-400° C. and then cooled to condense pyrolysates into the resultant char.
U.S. Pat. No. 7,544,635 issued Jun. 9, 2009 to Liang et al. for “Process for Changing Hydrophilic/Hydrophobic Characteristics” discloses a method for producing a material with modified hydrophilic/hydrophobic characteristics by pre-treating a biomass sample by soaking in water, alkaline/acidic reagents, expanding agents, or by freezing. The material is then oxidized in either air or a more powerful oxidizing atmosphere such as oxygen, ozone, or hydrogen peroxide. This method differs from the method of the present invention in a number of meaningful ways, the first being that the material is chemically pre-treated before undergoing pyrolysis rather than being treated in the cooling phase after pyrolysis. This is important because moisture in the reaction increases the need for external energy to drive the reaction. Secondly, in the process of the '635 patent, the material is reacted in an atmosphere having an oxidation number at least as high or higher than atmospheric air. The process described herein, however, reacts the material in an environment with an oxidation number below that of atmospheric air. Advantageously, having a lower oxidation number atmosphere reduces the carbon lost from a parent material in pyrolysis, resulting in a higher yield of material and a generally more hydrophobic product.
In view of the foregoing, it is apparent that a need exists for a new and useful material which is well suited for the removal, remediation, or sequestration of oil and oil-like chemicals from water and which can be used to repair environmental damages caused by such chemicals.